As was previewed in the months leading up to trial, prosecutors said Zimmerman was a vigilante who profiled Martin and took the law into his own hands, while the defense said it was Martin who "viciously" attacked Zimmerman and Zimmerman acted in self-defense.

With that here are three highlights that tell the story of the opening day:

-- The Knock, Knock Joke: Defense attorney Don West included a joke in his opening. As The Orlando Sentinel reports, first he told jurors there were "no monsters" in this case and then the Sentinel reports:

"... he told an ill-received knock-knock joke: George Zimmerman who? 'Alright, good. You're on the jury.'

"'[Expletive] punks. Those [expletives], they always get away,'" said assistant state attorney John Guy as he stood in front of the packed court, using the same words that he says Zimmerman told a police dispatcher as he pursued Martin on the night of February 26, 2012. "Those were the words in that grown man's mouth as he followed in the dark a 17-year-old boy who he didn't know ... Those were the words in that man's chest when he got out of his car armed with a loaded semi-automatic pistol and two flashlights to follow on foot Trayvon Benjamin Martin, who was walking home from a 7-Eleven ... Those were the words in that defendant's head moments before he pressed that pistol into Trayvon Martin's chest and pulled that trigger."

-- The Scream For Help: One of the keys in this case will likely be who the jury believes was heard screaming for help during a 9-11 phone call.

"Zimmerman's family members and friends have listened to the 911 recording and are convinced 'that's George Zimmerman screaming for help,' West said.

"'You cannot tell someones age by [listening to them scream],' West said. 'There's nothing predictable. A 50-year-old man can sound like a 15-year-old girl, so there's nothing scientifically there to tell who's voice it is.'"

"... prosecutor John Guy implied that it may have been Trayvon Martin screaming in the background of the call.

"'Listen carefully please, to that call. Listen carefully ... when the gunshot goes off, Trayvon Martin was silenced immediately,' Guy said. "When the bullet the defendant fired passed through his heart, when that gunshot rings out on the 911 call, the screaming stops.'"